Document DE 198 11 574 A1 describes a method for checking the serviceability of the catalytic converter of an internal combustion engine. In this method the degree of conversion is determined as a function of the temperature of the catalytic converter in heating operation, since with increasing age of the catalytic converter the relationship changes between the degree of conversion and the temperatures, by which the catalytic converter can be checked.
Document DE 43 38 547 A1 discloses monitoring a catalytic converter in a motor vehicle using the temperature distribution, the temperature distribution being detected by a sensor element which is oriented in the longitudinal direction of the catalytic converter. Since the temperature distribution is influenced by the exothermally proceeding pollutant conversion, the conversion capacity can be assessed by way of the temperature distribution.
Document DE 41 00 397 C2 discloses another method for monitoring the degree of conversion of a catalytic converter. This method calls for measuring the temperature values of sites on the catalytic converter with different temperatures during coasting phases of the internal combustion engine and comparing the to one another and using the resulting comparison value to obtain a monitoring signal.
Finally document DE 102 22 223 A1 discloses a method for monitoring and controlling a catalytic converter of an internal combustion engine in which the axial temperature distribution within the catalytic converter is computed, the computed axial temperature distribution at least one site being compared to measured values and constituting a measure of the activity of the catalytic converter from the difference resulting from the comparison, and when a given activity threshold is not reached, an OBD function is activated.
In this context, the object of this invention is to make available a further improved method for diagnosis which allows not only an integrated assessment of the storage capacity, and thus the conversion performance, but a differentiated assessment which in case of damage indicates the axial position and the region of the damage of the storage unit. This is because depending on where the damage is located within the catalytic converter, it acts differently on the conversion performance.